From a8502b67d739c1d7a4542c1da0a5d98a6a58c177 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 29 Jul 2016 09:30:13 -0700 Subject: [PATCH] x86/pkeys: Make mprotect_key() mask off additional vm_flags Today, mprotect() takes 4 bits of data: PROT_READ/WRITE/EXEC/NONE. Three of those bits: READ/WRITE/EXEC get translated directly in to vma->vm_flags by calc_vm_prot_bits(). If a bit is unset in mprotect()'s 'prot' argument then it must be cleared in vma->vm_flags during the mprotect() call. We do this clearing today by first calculating the VMA flags we want set, then clearing the ones we do not want to inherit from the original VMA: vm_flags = calc_vm_prot_bits(prot, key); ... newflags = vm_flags; newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); However, we *also* want to mask off the original VMA's vm_flags in which we store the protection key. To do that, this patch adds a new macro: ARCH_VM_PKEY_FLAGS which allows the architecture to specify additional bits that it would like cleared. We use that to ensure that the VM_PKEY_BIT* bits get cleared. Signed-off-by: Dave Hansen Acked-by: Mel Gorman Reviewed-by: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: Dave Hansen Cc: arnd@arndb.de Cc: linux-api@vger.kernel.org Cc: linux-mm@kvack.org Cc: luto@kernel.org Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/20160729163013.E48D6981@viggo.jf.intel.com Signed-off-by: Thomas Gleixner --- arch/x86/include/asm/pkeys.h | 2 ++ include/linux/pkeys.h | 1 + mm/mprotect.c | 11 ++++++++++- 3 files changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h index 33777c291a85..666ffc862ef7 100644 --- a/arch/x86/include/asm/pkeys.h +++ b/arch/x86/include/asm/pkeys.h @@ -38,4 +38,6 @@ static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma, extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long init_val); +#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | VM_PKEY_BIT3) + #endif /*_ASM_X86_PKEYS_H */ diff --git a/include/linux/pkeys.h b/include/linux/pkeys.h index 0030b4024559..6899b0bc7ce0 100644 --- a/include/linux/pkeys.h +++ b/include/linux/pkeys.h @@ -16,6 +16,7 @@ #define execute_only_pkey(mm) (0) #define arch_override_mprotect_pkey(vma, prot, pkey) (0) #define PKEY_DEDICATED_EXECUTE_ONLY 0 +#define ARCH_VM_PKEY_FLAGS 0 #endif /* ! CONFIG_ARCH_HAS_PKEYS */ #endif /* _LINUX_PKEYS_H */ diff --git a/mm/mprotect.c b/mm/mprotect.c index dd3f40a2935f..abd9c8257b2e 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -417,6 +417,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len, prev = vma; for (nstart = start ; ; ) { + unsigned long mask_off_old_flags; unsigned long newflags; int new_vma_pkey; @@ -426,9 +427,17 @@ static int do_mprotect_pkey(unsigned long start, size_t len, if (rier && (vma->vm_flags & VM_MAYEXEC)) prot |= PROT_EXEC; + /* + * Each mprotect() call explicitly passes r/w/x permissions. + * If a permission is not passed to mprotect(), it must be + * cleared from the VMA. + */ + mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC | + ARCH_VM_PKEY_FLAGS; + new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey); newflags = calc_vm_prot_bits(prot, new_vma_pkey); - newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); + newflags |= (vma->vm_flags & ~mask_off_old_flags); /* newflags >> 4 shift VM_MAY% in place of VM_% */ if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {